1. Field of the Invention
The present invention relates to a mirror support device and an optical scanning apparatus using the mirror support device. More particularly, the present invention relates to a mirror support device for stably mounting a mirror that reflects incident light in an optical scanning apparatus.
2. Description of the Related Art
Optical scanning apparatuses, such as laser scanning units (LSUs), are widely used for image forming devices and image reading devices such as digital copiers, electrophotographic image forming apparatuses, facsimiles, and barcode readers. In an optical system, the optical scanning apparatus uses a mirror to direct light to a desired location. Therefore, the optical scanning apparatus has a mirror support device to support the mirror and control the reflection of light by the mirror.
FIG. 1 is a partial exploded perspective view of a conventional mirror support device, and FIG. 2 is a partial side view, partially cut away, of the mirror support device depicted in FIG. 1. Referring to FIGS. 1 and 2, a mirror support device includes a mirror 5, a frame 10, and an elastic member 40. The mirror 5 reflects incident light to a desired location.
The frame 10 includes a mounting surface 12, a supporting surface 13, and a guide 14. The mounting surface 12 is sloped, and the mirror 5 is laid on the sloped mounting surface 12. The supporting surface 13 is located under the mounting surface 12 and is substantially perpendicular to the mounting surface 12 to support the bottom of the mirror 5 and prevent the mirror 5 from slipping down. The guide 14 protrudes from the top of the frame 10. The guide 14 couples with a guide hole 42 of the elastic member 40. That is, the guide 14 determines the installation location of the elastic member 40. Also, the frame 10 has a coupling hole 18 on its top. The coupling hole 18 is spaced apart from the guide 14 and is aligned with a coupling hole 44 of the elastic member 40. A coupling member, such as a screw (not shown), may be secured in the coupling hole 18 through the coupling hole 44 to fix the elastic member 40 to the frame 10.
The elastic member 40 has one end fixed at the top of the frame 10. The other end of the elastic member urges the mirror 5 toward the mounting surface 12. That is, the elastic member 40 biases the mirror 5 to the mounting surface 12 to elastically fix the mirror 5 to the frame 10. The shape of the elastic member 40 corresponds to the shape of the frame 10 so that the elastic member 40 can effectively hold the mirror without interfering with other parts. The elastic member 40 has a pressing portion 50 at the distal end. The pressing portion 50 makes contact along a single line with the mirror 5 when the elastic member 40 presses the mirror against the mounting surface 12.
As described above, the mirror 5 contacts the pressing portion 50 of the elastic member 40 when it is fixed to the mounting surface 12 of the frame. An arrow in FIG. 2 shows the direction of the pressing force acting on the mirror 5 by the elastic member 40. That is, the mirror 5 receives the pressing force only along a single contact line when it is fixed on the frame 10.
Since the pressing force of elastic member 40 acts only on a portion of the mirror 5 when the mirror 5 is fixed to the frame 10, the mirror 5 can be moved by impact. Also, since the pressing force of the elastic member 40 acts only along a single contact line between the pressing portion 50 and the mirror 5, the pressing force does not press effectively enough on the mirror 5, which allows the mirror 5 to deviate from its proper position when it is impacted.
Further, the conventional mirror support device does not deal effectively with machining errors in the mounting surface 12. That is, the mirror 5 may be separated from the mounting surface 12 or may receive the pressing force ineffectively. This causes the mirror 5 to vibrate and move from a proper position and thereby results in light scanning errors and image quality degradation.
Accordingly, there is a need for an improved mirror support device, and an optical scanning unit that uses the improved mirror support device.